(1) Field of the Invention
This invention relates to a periphery exposing apparatus and methods for exposing edge regions (peripheries) of photo-sensitive layers applied to surfaces of substrates such as semiconductor wafers.
(2) Description of the Related Art
In a process of manufacturing semiconductor devices, a resist solution is spin-coated a substrate such as a semiconductor wafer and developed into a predetermined pattern to form a resist mask. The resist mask is thereafter used to form film patterns.
The substrate which has been spin-coated with the resist solution is transported by gripping it at its edge regions and moving it thereof from one type of substrate treating apparatus to another. The resist solution, however, has been spread to the edge regions of the substrate by the spin coating step. Thus, when the edge regions of the substrate are gripped, the resist is separates from the edge regions, scatters and contaminates a resist surface in a central region of the substrate and other substrate surfaces. This could reduce the yield of substrate processing.
In the case of a positive type resist, the resist in the edge regions of a substrate is exposed, in advance by using a periphery exposing apparatus. Unwanted parts of the resist are removed from the edge regions of the substrate at the time of of the resist pattern development.
A conventional periphery exposing apparatus employs a method of exposing an annular region of fixed width from the outer edge of a substrate. Such a periphery exposing apparatus mechanically detects the position of an orientation flat or notch of the substrate by using a cam placed in contact the outer edge of the substrate. The orientation flat or notch is used as a reference for determining the annular region of fixed width from the outer edge of the substrate, and then the annular region is exposed.
Another type of conventional apparatus optically detects an orientation flat or notch of a substrate by using a line sensor. Here again, the orientation flat or notch is used as a reference for determining an annular peripheral region of fixed width, and then the annular region is exposed.
In recent years, there has been an increasing desire to remove unwanted resist from edge regions of a substrate more thoroughly in order to prevent, with increased assurance, contamination by particles scattering from the resist.
In another conventional scheme, a plurality of rectangular chips are formed on the substrate. The chips in an array (i.e. a chip region) describe a staggered or stepped outline while, the substrate or wafer is substantially circular. Simply exposing the peripheral region of fixed width from the outer edge of the substrate would leave unwanted resist in areas between this region and the stepped outline of the chip region.
A periphery exposing apparatus has been proposed which is capable of exposing the peripheral region along the stepped outline of the chip region. This conventional apparatus acquires, and stores in memory, position data of the stepped peripheral region along the outline of the chip region in advance. Based on the position data, an irradiator is shifted in two orthogonal directions for irradiating, with light, the substrate supported by a substrate supporting mechanism. In this way, the peripheral region is exposed in a staggered way along the outline of the chip region.
However, the following inconveniences are encountered with the conventional apparatus for exposing the peripheral region in a staggered way. The position data of the stepped peripheral region stored in advance are determined according to the chip region. Each chip in the chip region is formed on the substrate, for example, with reference to the orientation flat of the substrate or the like. On the other hand, the irradiator is shifted in the two orthogonal directions by a shifting mechanism disposed adjacent the substrate supporting mechanism. When the substrate is supported by the substrate supporting mechanism, a deviation may occur in a positional relationship between the orientation flat of the substrate and the shifting mechanism. Consequently, the two orthogonal directions in which the irradiator is moved do not always concur with the stepped outline of the chip region actually formed on the substrate. With such a deviation between the irradiator and the substrate supported by the substrate supporting mechanism, the peripheral region cannot be exposed along the stepped outline of the chip region with high precision.
Another drawback is that the positions of chips actually formed on the substrate (i.e. the position of the outline of the chip region on the substrate) may vary from substrate to substrate. In this case, the peripheral exposure region of each substrate deviates from the position data of the peripheral region stored in advance. This results in a defective periphery exposure which exposes even indispensable portions of the resist on the chips or leaves portions that should be removed. In addition, it is a troublesome operation to acquire and store the positional data of the peripheral exposure region in advance, which is no small burden on the operator.